Ultra high frequency signaling system



March 25, 1941. K. G. MacLEAN 2,236,004

ULTRA HIGH FREQUENCY SIGNALINGSYSTEM Filed July 50, 1958 5 Sheets-Sheet1 90M 1 E AMP I AMEN/WV AND DETEC'TO RS fi /31%;? 1 49" .1 I

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KEN? 6. MAC LEAN' ATTORNEY.

March 25, 1941. K. G, MacLEAN 2,236,004

ULTRA HIGH FREQUENCY SIGNALING SYSTEM Filed July so, 1938 s Shets-Sheet2 r0 ANTENNA MOVABLE UNIT f I H I! 43 2 05750701? CONCE/VI'R/C LIA/E 446 4 9 s1 9 AMPLIFIER OSCILLATOR CONCENTRIC L/NE F/XED UNIT INVENTOR.

' KENNETH GMAICLEAN March 25, 1941. K MacLEAN 2,236,004

ULTRA HIGH FREQUENCY SIGNALING SYSTEM Filed July 30, 19158 5Sheets-Sheet 5 rllllllllllllld m WJ J m mm m N w!= ====a\ gm mm ms W P WW A TTORN E Y.

Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE Kenneth G. MacLean,Riverhead, N.

to Radio Corporation of Delaware Y., assignor of America, a corporationApplication July 30, 1938, Serial No. 222,104

4 Claims.

This invention relates generally to receiving systems for the receptionof ultra high frequency signals. More particularly, the inventionrelates to the high frequency unit of a superheterodyne receiver capableof receiving waves of the order of SO centimeters in length.

One of the objects of the present-invention is to provide a highfrequency converter unit for an ultra short wave receiver capable ofreceivin signals in the range of 200 megacycles to 500 megacycles,wherein the tuning elements are adjustable and so arranged that theconnections to the vacuum tube electrodes are reduced to a mini mumlength.

Various features of the present invention lie in the novel mechanicalconstruction of the high frequency converter unit which enables theachievement of the foregoing object. This novel mechanical constructionincludes the use of 20 square metallic tubing, novel condenser unitswhich prevent leakage between shielded compartments, and concentric lineresonators used as tuned oscillatory circuits, etc. Another featureresides in the use of a novel concentric reso- 25 nant line controlledoscillator wherein the anode of a vacuum tube is grounded for radiofrequency energy, and reactance in the cathode to ground circuit isemployed to obtain the proper phase relations on the electrodes of thetube. This circuit differs from prior art filament tuning where thefilament is so tuned as to effectively be at ground potential. In thisnew circuit the filament is at high radio frequency potential and thereactance of the tuning element to ground constitutes a phase adjustmentof the cathode potential. Other objects, features and their advantageswill appear in the following description, which is accompanied bydrawings, wherein like parts throughout the figures are represented bylike reference characters. In the drawings:

Fig. 1 illustrates, schematically, the electrical features of a completesuperheterodyne receiving system embodying the principles of the presentinvention;

Fig. 2 illustrates only certain essential details of the physicalembodiment of the high frequency converter unit of Fig. 1, and shows insome detail the novel mechanical construction which goes to make up thevarious features of applicant's invention;

Fig. 2a shows the complete assembly of the high frequency converter unitof Fig. 2 with the front cover removed;

Fig. 3 is a detail cross-section view of the con- (Cl. ZED-36) centricline resonator used in the detector and oscillator circuits of theimproved high frequency converter unit;

Fig. 4 and Fig. 4a are perspective and side views, respectively, of thecollar type of connector used for coupling the inner conductor of theconcentric line to its associated circuit; and

Fig. 5 illustrates, very schematically, the equivalent electricalcircuit of the local oscillator of the high frequency converter unit,and is given for a better understanding of the principles involved.

Referring to Fig. l which indicates schematically the electrical circuitof a complete superheterodyne receiver employing my improved highfrequency converter unit, there is shown conventionally a detector I5 towhose grid is fed the incoming signal energy arriving from an antennaand transmission line I and to whose cathode is supplied oscillatoryenergy from a local high frequency oscillator I4. Both the detector andthe oscillator have associated therewith concentric line resonatorcircuits 2 and 3 respectively, each having an outer conductor 5 and aninner conductor 4, the inner conductor including as a portion thereof atube 6 which slides therein for tuning purposes. The output I9 of thedetector, which is tuned to the beat frequency of the incoming signalwave and the local oscillator frequency, is fed to an intermediatefrequency amplifier and detector 30 from which energy of a lowerintermediate frequency produced by beating with a second localoscillator 3|, is fed to a second intermediate frequency amplifier 32.From amplifier 32 the energy is passed on to a final detector 33 fromwhich there is obtained an audio frequency signal which is amplified in34 before utilization.

An inspection of the detector unit I5 will show that there is includedin each leg of the filament thereof a filter unit comprisin choke coilsI8 and low inductance filter condensers ll, of which more will be saidlater in connection with the description of Fig. 2. In the anode oroutput circuit I9 of detector I5 there are also included filter unitscomprising resistances R2 and R3 serially arranged in connection withlow inductance filter condensers IT. The anode and filament circuits ofoscillator unit I 4 are also similarly provided with filter circuits,generally of the same type shown in connection with the detector unit.It should be noted, however, that in the anode circuit of the oscillatorI4 there are provided three resistances R5, R6 and R7, instead of two,as shown in the anode circuit of the detector. The filter elements ofthe detector unit l5 and the oscillator unit l4 are divided intoshielded compartments, and the vacuum tubes per so are also shielded,both from th shielded elements of the filter units and from theassociated concentric line tuned circuits. The cathode of the detectorI5 is connected to the oscillator concentric line through a biasresistor R1 and condenser combination.

The oscillator 14, it should be observed, comprises a vacuum tube whoseanode is grounded to the outer conductor 5 of the concentric lineoscillatory circuit through a by-pass condenser 25 and whose gridelectrode is coupled through a grid-leak R4 and a coupling condenser 2 2to the inner conductor 4 of its associated concentric line resonator 3,the latter functioning as a frequency controlling element. There isprovided in circuit with the oscillator cathode a regenerative tuningcoil 26. By varying the inductance of coil 26, regeneration in theoscillator is obtained for optimum oscillation, while stability ofoscillation is controlled by varying the connec tion from the oscillatorgrid to the inner conductor 4 of the concentric line 3. In practice, (aswill be observed more fully from Fig. 2, the cathode regenerationcontrol is a coil of copper tubing within which the filament heatingleads are run to an external source of heating supply, tuning of thecoil being effected by inserting or withdrawing a solid metallic screwplug 28 within the spiral turns of the coil. It is obvious that thecathode to ground element may be any type of circuit presenting a properreactance to the oscillator frequency.

A better understanding of the operation of the oscillator l4 may be hadby referring to Fig. 5, which shows very generally the electricalarrangement of the grid, cathode, and anode electrodes of theoscillator. It will be observed that the anode is directly grounded forradio frequency energy. The by-pass condenser 25 of Fig. 1 has beenshown omitted in Fig. 5 for the sake of simplicity. The cathoderegeneration control is indicated by the variable regeneration controlcoil 26, which connects with ground and provides the proper phaserelations for oscillation. The coil 4' in Fig. 5, shown connectedbetween the grid and anode, is equivalent to the inductance of the tunedconcentric line circuit 3 of Fig. 1, particularly that portion betweenthe tapping point on. the inner conductor 4 which couples with the gridand the grounded outer conductor. It will be apparent that the circuitsimulates a Hartley type of oscillator.

This particular type of oscillator arrangement is highly advantageousand convenient, since it eliminates the necessity of a low inductancecathode lead and is non-critical in permitting tuning of the oscillatorover a wide range of frequencies without readjustments. Anotheradvantage lies in the elimination of a tuned anode circuit, such as iscustomary in certain known types of oscillators, thus simplifying theconstruction of the vacuum tube circuit and eliminating the necessityfor running a low inductance lead from the anode or the cathode of thetube to the tuned circuit. A further advantage of the improvedoscillator circuit M is that the construction provides an easy method offiltering the anode supply, and only requires a single connection fromthe oscillator vacuum tube to the concentric line 3. It is obvious thata further modification of this circuit which would operate the samewould consist of grounding the grid and readily accessible from thefront.

connecting the plate only to the concentric line, the cathode reactanceremaining the same. A still further advantage is that the amount ofreactance between the grid and plate of the oscillator and ground iskept extremely small so as to discourage parasitic oscillations at thehigher frequencies.

The operation of the circuit of Fig. 1 will now be described briefly.The signal from the antenna is passed into the detector concentric line2 by conductively coupled transmission line l. The detector concentricresonant line 2 is then tuned to the resonant frequency of the receivedsignal, let us say 500 megacycles, and the grid of the detector 55 isadjusted on the inner conductcr i of the resonant line 2 for optimumresults. The cathode of the detector l5 which is connected through biasresistor R1 and the condenser combination to the inner conductor 4 ofthe oscillator resonant line 3 is adjusted for proper excitation of thedetector, and the oscillator Hi is tuned say 90 megacycles higher orlower than the signal frequency to provide a suitable intermediatefrequency of QOmegacycles in the tuned output it of the detector. Thetwo frequencies of 500 mega-cycles (the incoming signal frequency) and41.0 megacycles (let us say the oscillator frequency) are mixed in thedetector i l and the resultant beat or converted frequency of 90megacycles is selected by the detector anode tuned circuit l9 and passedon to the first intermediate frequency amplifier 30 by means of a lowimpedance coupled circuit. From the first intermediate frequencydetector circuit 30 a lower beat note of 5.5 megacycles is passed on tothe second intermediate frequency amplifier. and from this latteramplifier the signal is passed to a final detector 33 from which audiofrequency energy is supplied to the audio frequency amplifier 34. Asecond local oscillator 3| serves to supply oscillations to the firstintermediate frequency detector circuit 33 to produce the second lowerintermediate frequency of 5.5 megacycles. The elements 3!), 3t, 32, 33and 34 have been shown conventionally in box form,

since such circuits are well known in the art and of themselves form nopart of the present invention, except that they couple, in the mannershown, to the high frequency converter unit l4, l5 to form anadvantageous combination of circuit elements. I

Fig. 2 illustrates only certain essential details .of the completeassembly of Fig. 2a. More specifically, Fig. 2 is a front View of thehigh frequency converter unit, with the front panel removed, in order toshow how all the equipment is The outer conductors 5 of each of theconcentric line tuned circuits 2 and 3, and the shielding for theoscillator i l. detector l5, and the associated filter elements are inthe form of square tubing since from a mechanical standpoint such squaretubing makes it very convenient to mount the elements on one another andto screw the covers for each This construction also of the elements inplace. enables adjustment of the parts relative to one another. Itshould be noted that the concentric line elements are integral elementsof themselves, which are adjustable and movable as a whole, relative tothe oscillator unit l4 and the detector unit It, which also with theirassociated filters are integral units adjustable relative to one anotherand to the concentric lines.

The detector and oscillator electrodes and the antenna transmission lineI all couple to the inner conductors l of the concentric lines by meansof collar type clamps 9 which surround the inner conductor and aremovable over the outer sur faces thereof by adjustment of the screws I0,shown in the collars. Figs. 4 and 4a, respectively, show perspective andcross-sectional views of the construction of the collars. It will beobserved from these figures that the collar comprises a circularclamping arrangement which is split at one end for clamping around theouter surface of the inner conductor. At the lower end of the clamp,there is provided a recessed or indented portion to which is securedanother recessed or indented plate II. Where it is required that therebe a condenser serially included in the connection of the collar to theassociated vacuum tube circuit, such as in the grid circuit of theoscillator I4, and in the cathode circuit of the detector l5, there isprovided a mica spacer 8 between the elements II and 9 so as to providea capacity efiect therebetween. In this last case, it will be obvious,of course, that screws II' will have bushings I2 provided for securingelements 9 and II together, in order to provide suitable insulationtherebetween. Of course, where there is no necessity to provide acondenser in series with the collar 9, to its associated circuit, therewill be no necessity for providing a mica spacer 8 between the elementsII and 9, and for this reason the element 9 may be made integral withthe element II so as to provide a direct conductive connectiontherebetween. Such an arrangement is used for the clamps coupling theantenna I and the grid of the detector I5 to the inner conductor 4 ofthe concentric resonant line 2. The connector 9 may be provided at itslower end, particularly in the portion II, with an insulating head 1, asshown in Figs. 2 3, 4 and 4a, in order to prevent possible contact ofthe sides of the metallic tubing with the element II as the clamp 9 isadjusted over the inner conductor of the resonant line. This bead I maybe made of Victron or any other suitable insulating material. Where thecollar 9 and element II have a dielectric spacer 8 in between forproviding a condenser effect, it is a relatively simple matter to solderacross both of these elements a small bias or grid leak resistor R1 orR4, as shown in Fig. 2, for the cathode circuit of detector I5 and forthe grid circuit of the oscillator I4 respectively.

The oscillator unit M with its associated filter elements R5, R5 and R7and condensers l1 and inductors I8 are movable as an integral unit, ineither direction longitudinally with respect to its associatedconcentric line 3, merely by loosening screws 35 (note Fig. 2a) whichfasten the square metallic tubing shielding the oscillator unit M to thesquare metallic tubing constituting the outer conductor 5 of theresonant line 3, and by loosening the screws Ill on the clamps 9.Similarly, the detector unit I5 and its associated filter circuits aremovable as an integral unit longitudinally in two directions withrespect to the resonant lines 2 and 3. The screws 35 used for securelyfastening the detector unit to the two resonant lines are also shown.

One of the novel features in the physical embodiment of the highfrequency converter unit lies in the use of the low inductance filtercondensers I l which comprise, in efiect, a pair of plates mounted onopposite sides of a dividing or partition wall. This partition wallseparates the filter elements into different compartments. The wall isprovided with a hole or aperture to enable the screw to pass through thepartition and to connect together the two plates on opposite sides ofthe hole. Since the partition wall and the square tubing in which thepartition wall is mounted is grounded, there are provided mica ordielectric spacers between each plate of the condenser I I and theimmediately adjacent partition wall to effectively insulate the platesfrom the partition. The screw passing through the aperture or hole inthe partition wall has a diameter smaller than the hole, and connectsboth plates of each condenser I! together, thus forming terminals forthe connecting wires. Such an arrangement eliminates the necessity ofusing separate leads between compartments in order to connect thecondenser elements to associated circuits. Furthermore, each plate ofthe condenser II forms through the dielectric spacer a low impedancepath to ground for the radio frequency energy. The screws connecting theplates together have extremely small reactances at the high frequenciesand serve as the mechanical mounting for the condenser. Since the holeor aperture in the partition wall is plugged to some extent by the screwconnecting the plates and condensers I! together, and the plates arerelatively large with respect to and cover both sides of the aperture inthe partition, it will be apparent that there can be no leakage betweencompartments because of the hole in the partition, inasmuch as the holeis effectively shielded by the condenser plates.

Fig. 3 shows, in some detail, the features of the concentric resonantline employed in the present invention. The inner and outer conductorsof the concentric line are conductively coupled together 3 at one end byan end plate 36. The inner conductor 6 includes an adjustable extensionpiece 31 which is longitudinally movable in response to rotation of theshaft 38. The shaft 38 is mounted in an insulating bearing 43 and isthreaded in the interior of the conductor 4 so as to cooperate with aninsulated threaded sleeve 39. Threaded sleeve 39 is pinned to extension3? while a split bronze sleeve 4|] is used to produce good electricalcontact between elements 31 and t. Keyways cut in the edge of 3! allowlongitudinal movement without rotation of the inner element 31. Shaft 38is driven through flexible couplings 44 by a tuning control knob 45 forrapid tuning or by disc 46 for fine tuning (note Fig. 2a). A counter 4|is geared to the shafting for use as an indicator, and reads, inaccordance with one actual embodiment constructed in accordance with theinvention, of a turn and from zero to 30 turns. The purpose of theflexible coupling 4 and the insulated bearing 43 is to avoid unnecessaryelectrical noise from sliding metallic contacts. A long shaft, such as42, may extend through coupling 44 so that the entire resonant controlline can be moved readily without disturbing the dial driving mechanism.In Fig. 3 there is also shown the collar clamp device 9 and a slot inthe outer conductor over the length of which the collar may be moved.

An inspection of Fig. 2 will show that the various electrodes of theoscillator and detector are suitably by-passed to ground where required,by means of their supporting metallic elements external of the vacuumtube, which in turn are mounted on suitable dielectric spacers, such asmica, in turn located adjacent the square tubing. For example, it willbe observed that the filaments and anode terminals of both oscillator I4and detector 15 are mounted. on metallic plates which are spaced fromthe supporting square tubing by means of insulating spacers so as toform by-pass condensers.

It should be noted that the metallic screw plug 28, which is employedfor short circuiting the turns of the cathode regeneration coil 26 ofthe oscillator unit I4, is movable by means of a suitable knob 41.

The term ground as used in the specification and the appended claims isdeemed to include any point of zero high frequency alternating currentpotential, as Well as an actual earthed connection.

What is claimed is:

1. An ultra high frequency oscillation generator comprising anindirectly heated vacuum tube oscillator having grid, anode and cathodeelectrodes, a heater for said cathode, a concentric line resonator forstabilizing the frequency of said oscillator, said resonator having aninner and an outer conductor suitably coupled together, a connectionfrom said outer conductor to ground, a capacitive connection from saidanode to ground for the radio frequency energy, a connection from saidgrid to a point on said inner conductor, a regeneration control coilcoupling said cathode to ground, leads within said coil coupling saidheater to an external source of energy, and means for tuning said coil.

2. An ultra high frequency oscillation generator comprising a vacuumtube oscillator having grid, anode and cathode electrodes, a heater forsaid cathode, a metallic shielding box surrounding said vacuum tube, aconnection from said shielding box to ground, a frequency stabilizingelement external of said box and coupled to the grid of said vacuumtube, a metallic plate mounted on the interior of said box and separatedtherefrom by a dielectric spacer to form a low impedance capacitive pathto ground for radio frequency energy, a connection from said metallicplate to said anode, a regeneration control coil for said oscillatorlocated within said box, said coil being hollow and connected at one endto said cathode and at its other end to said box, leads within said coilcoupling said heater to an external source of heating supply, a leadextending from said anode to a source of polarizing potential locatedexternally of said box, and means for by-passing said heater leads toground where they emerge from both ends of said coil.

3. An ultra high frequency oscillation generator comprising a vacuumtube oscillator having grid, anode and cathode electrodes, a metallicshielding box surrounding said vacuum tube, a connection from saidshielding box to ground, a concentric line resonator located externallyof said box, said resonator having an inner and an outer conductorsuitably coupled together, said outer conductor being in contact withsaid box and movable relative thereto, a connection from a point on saidinner conductor intermediate its ends to the grid of said vacuum tubeoscillator, a capacitive connection from said anode to said box, and aregeneration control coil within said box coupling said cathode toground, said coil having means for tuning the same.

4. An ultra high frequency oscillation generator comprising a vacuumtube oscillator having grid, anode and cathode electrodes, a heater forsaid cathode, a metallic shielding box surrounding said vacuum tube, aconnection from said shielding box to ground, a frequency stabilizingelement external of said box and coupled to the grid of said vacuumtube, a metallic plate mounted on the interior of said box and separatedtherefrom by a dielectric spacer to form a low impedance capacitive pathto ground for radio frequency energy, a connection from said metallicplate to said anode, a regeneration control coil for said oscillatorlocated within said box, said coil being hollow and connected at one endto said cathode and at its other end to said box, leads within said coilcoupling said heater to an external source of heating supply, a leadextending from said anode to a source of polarizing potential locatedexternally of said box, filter elements in circuit with each of saidheater leads and with said anode lead and located externally of saidbox, and means in circuit with each lead to said box for grounding saidfilter elements for radio frequency energy, said means comprising ametallic plate on each side of one wall of said box and separated fromsaid wall by a dielectric spacer, and a screw electrically connectingsaid last plates together through an aperture in said wall.

KENNETH G. MACLEAN.

